Artifacts at 4.5 and 8.0 Microns in Short-Wavelength Spectra from the Infrared Space Observatory

Abstract

Spectra from the Short-Wavelength Spectrometer (SWS) on board the Infrared Space Observatory exhibit artifacts at 4.5 and 8 μm. These artifacts appear in spectra from a recent data release, OLP 10.0, as spurious broad emission features in the spectra of stars earlier than approximately F0, such as α CMa. Comparison of absolutely calibrated spectra of standard stars to corresponding spectra from the SWS reveals that these artifacts result from an underestimation of the strength of the CO and SiO molecular bands in the spectra of sources used as calibrators by the SWS. Although OLP 10.0 was intended to be the final data release, these findings have led to an additional release addressing this issue, OLP 10.1, which corrects the artifacts. Based on observations with the Infrared Space Observatory, a European Space Agency (ESA) project with instruments funded by ESA member states (especially the principal investigator countries: France, Germany, the Netherlands, and the UK) and with the participation of the Institute of Space and Astronautical Science and the National Aeronautics and Space Administration (NASA).